#include <stdio.h>

int main() {

    int n;
    enum {
        sun, mon, tue, wed, thu, fri, sat
    } day;
    char weekday[7][4] = {"sun",
                          "mon",
                          "tue",
                          "wed",
                          "thu",
                          "fri",
                          "sat"};
    printf("输入间隔天数:");
    scanf("%d", &n);
    day = sun;
    printf("今天是%s,%d天后是%s.\n", weekday[day],
           n, weekday[(day + n) % 7]);

}